Technical progress in agriculture continues to bring advancement in planters and the seeds they sow. Towed behind a tractor, planters are machines for drilling crops such as maize (corn), soybean, sugarbeet, cotton, oil seed rape (canola) and sunflower. Planters open a sowing furrow of desired depth, drill (sow) seed into the furrow, then close the furrow covering the seed with soil. Many planters use vacuum systems whereby a fan or turbine generates a vacuum which pulls a seed toward a planting disk and holds it against a suitably-sized hole in the disk. When the disk rotates to the desired position the vacuum is released, allowing metered passage of seeds which is a component of accurate drilling. Such technology is sometimes referred to as pneumatic planting and is well known in the art, see U.S. Pat. No. 5,170,909.
Seeds represent a considerable investment to a grower, to protect them until sowing and offer the best possible conditions for early plant development they can be provided with a seed dressing or treatment. Seed treatments often include agrochemicals such as insecticides and fungicides as well as adhering and/or coating agents intended to hold the seed treatment components on the seed. For various reasons the seed treatment can fail to form a coherent layer which remains intact through processing, storage, transport and drilling.
One consequence of the use of a vacuum during the drilling process is that there is exhaust air to release into the surroundings. Untreated seeds which have not been suitably cleaned generate dust and debris which is carried in the exhaust air. Likewise waste is present in the exhaust air from treated seeds, whether due to a less than optimal seed treatment or simply because of abrasion during transport, storage and loading of seeds into the hopper. While the dust and debris from untreated seeds is unsightly but typically not dangerous, fragments of coatings or dust from treated seed can potentially be harmful to humans, animals and insects in the immediate vicinity of the drilling, as well as to the local environment in general.
Early planters exhausted outlet air into the atmosphere above or beside the planter, but this was not ideal. An improvement was to deflect outlet air toward the soil surface. Larger or heavier debris might remain in place on the soil, but even when the deflector was positioned behind the furrow opener dust, especially fine particle dust, was still measurable around the planter.
It has been recommended to direct the outlet air into a tube or similar device which is positioned below the soil surface, channeling outlet air into the field. The tube creates an indentation which is like an additional furrow. A device provided under the trade name SWEEPAIR separates dust from air and diverts the dust into the ground.
It has also been proposed to recirculate the exhaust air into the vacuum drilling system, releasing toward the ground only that which is necessary to keep the system temperature suitable, see U.S. Pat. No. 8,443,742. An improvement on this technology described in WO 2012/029003 is to filter the small portion of air which is released. A standard air filter can be provided to a pressure compensation chamber for the recirculating air, to prevent dispersion of dust contained in the chamber when air is released therefrom.
Despite advances in the art, there remains a need for alternative options for drilling seeds in a safe and environmentally-friendly manner, which address the problems associated with known methods.